The invention relates to an installation for and a method of drying or ripening foodstuffs, particularly meat products, by means of unsaturated air, with a processing room comprising a supply air duct and a waste air duct, the supply air duct being connected to an outside air supply, having a cooler, a heater and a fan, and being connected to the processing room via an air inlet duct.
For ripening and drying foodstuffs, particularly meat products, such as smoked bacon, etc., such installations are used in which particularly a gradual extraction of humidity takes place by means of conditioned air. The ripening or drying conditions are ascertained thereby from empirical values which vary according to product and region.
In order to make the process air suitable for the continuous absorption of humidity, it must first be de-humidified; this means that dry air must be fed in and moist air discharged. The rate of drying ought thereby to be governed by that water yield capacity of the substances being processed which does not produce any variations in quality. Excessive drying causes hardening of the marginal areas, the water conductivity of which drops in consequence, so that drying in the interior is impaired. Excessively slow drying, on the other hand, increases the danger of rotting and mould formation. Temperature and moisture content of the supplied air must therefore be adjusted according to the degree of drying and maturity, this being performed in a time and energy saving manner on grounds of economy. Tests along these lines were disclosed by DE-OS 34 12 107 and DE-OS 35 14 693. According to DE-OS 34 12 107 and DE-OS 35 14 693, the moisture and the temperature in the processing room are measured during processing and compared with desired values and in order to adapt the supply air to these desired values, ambient air is admixed with waste air so long as the ambient air is suitable for attaining the desired values. Cooling, heating and humidifying are only initiated when the outside air is no longer suitable. The process room in which temperature and humidity sensors are disposed comprises, for carrying out this method, one supply air duct and two waste air ducts, the first of which discharges into the supply air duct which has a closable outside air connection, while the second waste air duct discharges into the free air. In the supply air duct, following the mouth of the waste air duct, there are the cooler, a mist collector, a humidifier, a heater and the fan. Since the pressure gradient between the pressure side and suction side of the fan is greater than between the pressure side and the outside air as well as the outside air and the suction side circulation of the air enjoys priority via the first waste air duct and the supply air duct, i.e. generally, the outside air can only be admixed to a degree which is dependent upon the pressure gradient, so that the maximum potential of the outside air cannot be fully exploited. Furthermore, humidity measurement in the process room is susceptible to problems. Even the most accurate humidity measuring instruments have measurement errors of up to 10% so that per se minimal humidity differences which have to be kept low between supply air and waste air and the start and finish of the processing of the substance being processed cannot be accurately measured.